Fuze for small caliber projectile



Feb. 19, 1957 w. J. DONAHUE, JR

FUZE FOR SMALL CALIBER PROJECTILE 2 Sheets-Sheet 1 Filed June 9, 1950 mm m. N 3 Q .m 3 N. NNRJI Q NY S VA vm i! H I r r 5U:- 8. 2 21 91 mmu m 5 2 mm Feb. 19, 1957 y w. J. DONAHUE, JR ,781,725

FUZE FOR SMALL CALIBER PROJECTILE Filed June 9, 1950 2 Sheets-Sheet 2 FIG.5.

3 wumvm W. J. DONAHUE, JR.

M. WI;

United States Patent This invention relates to a fuze and more particularly to a bore safe base fuze for use in a projectile such, for example, as the type known to those skilled in the art as a 20 millimeter type projectile. v

Heretofore, fuzes of this type did not provide detonator bore safety mechanisms for preventing inadvertent explosion of the projectile within the muzzle of the gun as the projectile was fired therefrom. Usually such fuzes were constructed and arranged in such a manner as not to incorporate maximum safety when used in 20 millimeter projectiles and fired from a small caliber gun for the reason that the detonator and firing pin within the fuze were disposed in alignment with the bursting charge arranged within the projectile and thus should the detonator be initiated as the gun was fired the resulting bore detonation thereof would fire the bursting charge and explode the projectile within the bore of the gun thereby causing severe damage to the gun or rendering the gun worthless for future use and possibly injuring the gun crew. Furthermore, fuzes of this type heretofore employed for use in 20 millimeter ammunition were not altogether satisfactory for the reasons that they were constructed in such a manner as to detract from the sensitivity of the fuze upon target impact due to the relative bulky and complicated construction of the anti-creep members involved therein.

The present invention provides a new and improved fuze structure for use with small caliber ammunition and constructed in such a manner as to overcome the aforesaid disadvantages existing in prior art devices. Furthermore, the fuze of the present invention provides a new and novel arrangement of the component parts thereof such as to provide a detonator bore safety feature, maximum sensitivity, high average impact performance, and simplicity thereby permitting mass production of the fuze rapidly and economically.

One of the objects of the invention is the provision of a new and improved base fuze for 20 millimeter ammunition having a detonator bore safety mechanism for preventing arming of the fuze until the projectile has been fired from a gun and traveled a predetermined distance from the muzzle thereof.

Another object is to provide a new and improved fuze having detonator bore safety mechanism for maintaining the fuze in a safe condition as the projectile is fired from a gun and in which means are employed for firing a movable detonator as the detonator is driven through an anti-creep device and into engagement with the firing means upon impact of the projectile with a target. Another object is to provide a new and improved fuze in which a frangible anti-creep device is employed for arresting the motion of the detonator as the detonator is moved forward by creep forces acting on the projectile as the projectile travels along the trajectory.

A further object is to provide a new and improved fuze in which a movable time delay detonator is releasably ICC value, and in which means are provided for initiating the detonator as the detonator is driven a predetermined amount forwardly in response to impact ,of the projectile with a target thereby to explode the projectile within the interior of the target in time delayed relation with respect to the impact of the projectile with the target.

A still further object is to provide a new and improved fuze for a 20 millimeter projectile in which a movable time delay detonator is provided for exploding theprojectile in time delayed relation with respect to impact of the projectile with a target, and in which means including a frangible anti-creep device is provided for preventing movement of the detonator into firing engagement with .a firing pin until the projectile strikes the target.

Still another object is to provide a new and improved fuze for a projectile which is economical to manufacture, reliable in operation, highly sensitive upon target impact, and possesses the qualities of durability and detonator safety during handling, firing and transportation.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

Fig. 1 is a fragmentary sectional view of a projectile employing the fuze of the present invention according to a preferred embodiment thereof with the fuze in an unarmed position;

Fig. 2 is a view similar to Fig. 1, with the fuze in a armed position;

Fig. 3 is a view similar to Fig. 2, with the fuze" in a firing position;

Fig. 4 is a sectional view taken on the line 44 of Fig. 1;

Fig. 5 is a sectional view taken on the line 5-5 of Fig. 1;

Fig. 6 is a detail end elevational view of the metal cup and firing pin formed thereon;

Fig. 7 is a sectional view taken on the line 77 of Fig. 6; and

Fig. 8 is a sectional view of an alternative form of the device of Fig. 1.

Referring now to the drawings wherein like reference numerals designate like parts throughout the several views and more particularly to Fig. 1 thereof, there is shown a projectile generally indicated by the numeral 10 and comprising an armor piercing shell 11 having secured thereto a casing 12. The casing 12 has disposed therein the usual explosive charge 13 adapted to propel the projectile from the casing 12 and through the bore of the gun, as is well known to those skilled in the art to which the invention pertains. The projectile is provided with an annular sleeve 14 of any material suitable for the purpose such, for example, as copper or the like adapted to be engaged by the rifling of the gun as the projectile is propelled outwardly therefrom by the firing of the explosion charge 13 within the casing 12 and thereby impart a rotary movement to the projectile about the axis thereof as the projectile moves through the bore of the gun. The projectile is thus adapted to be propelled along a trajectory and to spin or rotate continuously about its axis throughout the trajectory as the result of the rotary movement imparted thereto by the rifling of the gun. Disposed within the cavity 15 formed in the shell 11 is a bursting charge 16 adapted to cause fragmentation of the shell 11 as the charge is fired.

The base fuze of the present invention employed with the aforesaid projectile is generally indicated by'the reference character 17 and comprises a casing 18 composed the projectile has reached substantially the maximum of any material suitable for the purpose such, for example, as steel, and having a centrally disposed bore or well 19 formed therein. As shown most clearly on Figs. 1, 2 and 3 the casing 18 is threaded into the cavity 15 formed in the shell 11 as at 21 and a sealing gasket 22 is disposed between a shoulder 23 formed on the casing 18 and one end of the shell 11 thereby to provide a sealed joint therebetween.

A rotor support generally indicated by the reference character 24 which may be made by a die casting process and composed of any material suitable for the purpose such, for example, as aluminum is arranged within the bore 19 of the casing 18 and comprises a body 25 having a recess 26 and a runway 27 formed therein, the runway bordering on the recess, Fig. 5.

Disposed within the recess 26 and preferably composed of brass or the like is a normally locked rotor 28 adapted to have rotative movement therein when released, the rotor being provided with a centrally disposed cavity or well 29. As shown on Fig. the rotor is locked against rotation within the recess 26 by a setback device 31 and a shear pin 32, the rotor being locked in the aforesaid manner until the shear pin is severed. The shear pin is composed of any metal suitable for the purpose such, for example, as copper and extends through registering openings 33-34 formed in the rotor and setback device respectively. The setback device or block is adapted to have sliding movement within the runway 27 so as to shear the pin 32 by the setback force received thereby as the projectile is fired whereupon the rotor is released from locking engagement with the block and thus the rotor is free for rotative movement within the recess 26 as a predetermined speed of rotation has been reached by the projectile when the projectile has traveled beyond the muzzle of the gun after being fired therefrom.

It will be understood, however, that when the pin 32 has been severed or sheared in response to the setback force received by the setback device 31 as the projectile is fired from the gun, the rotor is released, but due to the aforesaid setback force acting thereon, the rotor will tend to bind against the walls defining the recess 26 and thus the binding action will prevent rotation of the rotor until the setback force decays sufliciently to permit free rotation of the rotor. When this occurs the rotor will be moved to an armed position, Fig. 2, in response to the force thereon when the projectile has reached a maximum speed of rotation.

Slideably arranged within the opening 29 of the rotor is a compound detonator 35- comprising a casing 36 having a plurality of explosive charges arranged therein such, for example, as the priming mixture 37, delay mixture 38, initiator charge 39, and the base charge 41. It will be understood, however, that the specific gravity of the casing 36 including the aforesaid explosive charges is less than the specific gravity of the surrounding material enclosing the detonator and thus a dynamic couple is produced by rotation of the shell suflicient to rotate the rotor to an armed position, Fig. 2, with the detonator in alignment with the rotational axis of the shell as the projectile passes beyond the muzzle of the gun.

Arranged within the cavity 15 and encased within the bursting charge 16 is an elongated metal cup-shaped device generally indicated by the numeral 42 comprising a cylindrical portion 43 having a wall 44 formed on one end thereof, and a flanged portion 45 formed on the other end. The wall 44 has formed thereon and struckout therefrom a firing pin 46, Fig. 7, the pin being in alignment with the detonator 35 when the fuze is in an armed position. The wall 44 has secured thereto a disc 47 composed of any material suitable for the purpose such, for example, as copper thereby sealing the opening therein caused by the formation of the firing pin. A disc 40 composed of felt, cork, paper, or the like, is arranged within the portion 43 of the device 42 and secured to the wall 44 for cushioning or absorbing the shock as the detonator is driven into firing engagement with the firing pin, the firing pin extending through an opening 48 formed in the disc and a predetermined amount into the portion 43 thereby to impinge and fire the detonator.

Arranged between an end of the block 24 and the flanged portion 45 is an anti-creep device generally indicated by the reference character 49 comprising an annular member 51 of substantially U-shaped configuration in cross section and preferably composed of suitable metal such, for example, as copper and having a frangible diaphragm 52 secured thereto, the diaphragm being composed of any material suitable for the purpose such, for example, as paper, plastic, metal or the like. It will be understood, that as the projectile leaves the muzzle of the gun, the safety mechanism moves to a position as heretofore described whereupon the detonator is free to move within the cavity 29 and will move forward by creep forces acting on the projectile and thus when the detonator has moved a predetermined amount the forward motion thereof is arrested by the anti-creep device and further movement thereof will not occur until the projectile strikes the target.

As shown on Figs. 1, 2 and 3 the block 24, diaphragm 52, and the device 42 are clamped to the fuze by a retaining nut or closure plug 53 threaded into the bore 19 as at 54, and into abutting engagement with the flanged portion 45 formed on the device 42 whereupon the aforesaid parts are secured to the fuze casing.

Disposed between the closure plug 53 and the bursting charge 16 is a disc or washer 55 having a centrally opening arranged therein through which the portion 43 of the device 42 snugly passes, the disc being composed of any material suitable for the purpose such, for example, as felt thereby to provide means for absorbing any shock to which the charge may be subjected and also preventing any shifting thereof within the cavity 15 and thus preventing premature firing of the charge during handling, transportation, and in service.

On Fig. 8 there is shown an alternative arrangement of the fuze, the casing 18 thereof is provided with a centrally disposed bore 56 in which the detonator 35 is slideably arranged in substantially abutting engagement with the diaphragm 52 of the anti-creep device 49.

The fuze is maintained in a safe position by an interrupter device 57 normally in alignment with the detonator and movably arranged within a support 58 secured to the casing 18 as by threading the parts together as at 59. The interrupter comprises a body portion 61 having one end thereof weighted as at 62 for effecting movement of the interrupter in response to centrifugal force as the speed of rotation of the shell reaches a predetermined value, the interrupter being slideably arranged within a transverse slot 63 formed in the reduced extension 64 on the support 53. The interrupter is held within the slot 63 by an annular split spring 65 in engagement therewith and disposed about and in engagement with the aforesaid extension'64 and thus movement of the interrupter will not occur until centrifugal force acting thereon due to rotation of the shell about its axis is of sufiicient strength to overcome the tension of spring 65 whereupon the interrupter is moved out of alignment with the detonator thereby arming the fuze.

In this form of the device the cup-shaped member 42 is secured to the fuze as by the closure plug 53 and is substantially the same construction as that disclosed in the preferred embodiment except that the firing pin 66 in this arrangement is formed from a separate piece of material and not struck-out from the wall 44 as is the case heretofore shown and described. The firing pin comprises a striker 67 disposed in alignment with the detonator and is secured to the wall 44 by an enlarged head 68 formed thereon and crimped into engagement therewith.

By the aforesaid arrangement it will be understood, that when the interrupter has been moved sufliciently in response to the aforesaid force the bore 69 arranged in the support 58 is unobstructed and thus upon impact of the projectile with a target the detonator will be forcibly driven through the diaphragm and into firing engagement with the striker 67 thereby exploding the projectile.

Briefly stated in summary, the present invention contemplates the provision of a new and improved highly sensitive base fuze for use in 20 millimeter ammunition having means responsive to the setback force as the gun is fired for releasing the arming device for movement to an armed position and the time delay detonator for movement to a firing position, movement of the arming device being restrained until the setback force has decayed suf ficiently and the projectile has reached a maximum speed of rotation after it leaves the muzzle of the gun, whereupon the detonator is arrested in alignment with the firing pin and maintained in spaced relation with respect thereto by a frangible anti-creep device until the projectile strikes the target and in which means are provided for exploding the projectile in predetermined time delayed relation with respect to impact of the projectile with a target thereby to permit penetration of the outer plates of the target by the projectile and explosion thereof within the interior structure of the target.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

1. A base fuze for an explosive shell comprising a casing, a rotor supported within the casing in a safe position and constructed and arranged to have rotative movement therein when the shell has been fired from a gun, a mass detachably secured to said rotor and slideable within said casing when detached from the rotor, a shear pin detachably securing said rotor to said mass for locking said rotor in said safe position and for releasing the rotor for movement to an armed position in response to centrifugal force when the pin is sheared in response to setback force of the mass as the shell is fired from a gun, a detonator arranged within said rotor and adapted to be driven to a firing position when the fuze is in said armed position and upon impact of the shell with the target, a frangible diaphragm secured to the casing in alignment with the detonator when the rotor is in said armed position for preventing movement of the detonator to said firing position in response to creep forces acting on the projectile as the projectile travels along a trajectory, a cylindrical member secured to the casing in alignment with said diaphragm and extending into a bursting charge arranged within said shell, an end wall on said cylindrical member in predetermined spaced relation with respect to said detonator and located in said firing position thereof, a firing pin secured to and struck-out from said end wall and extending into said cylindrical member for firing said detonator when the detonator is forcibly driven through said diaphragm and into engagement with said pin in response to said impact, and means arranged within said detonator and fired thereby for firing the bursting charge in time delayed relation with respect to said impact,

2. A fuze for an explosive shell comprising a casing, a rotor support clamped within said casing, means including a member in threaded engagement with said casing for clamping the rotor support thereto, a rotor arranged within said rotor support for rotative movement to an armed position by centrifugal force as the shell rotates, a time delay detonator arranged within said rotor for movement to a firing position when the rotor is in said armed position and upon impact of the shell with a target, a mass detachably secured to the rotor and slideable within said rotor support when detached from the rotor, a pin for releasably securing the mass to said rotor and constructed and arranged to lock the rotor in an unarmed position within the rotor block until the pin is sheared by the setback force of the mass as the shell is fired from gun, a frangible diaphragm secured to the casing in alignment with the detonator when the rotor is in said armed position for preventing movement of the detonator to said firing position in response to creep forces acting on the shell as the shell travels along a trajectory, a cup-shaped member secured to the casing by said clamping member in alignment with said diaphragm and extending into a bursting charge arranged within said shell, an end wall on said cup-shaped member in predetermined spaced relation with respect to said detonator and diaphragm and located in said firing position of the detonator, and a firing pin struck-out from said end wall and extending into said cup-shaped member for firing said detonator when the detonator is forcibly driven through said diaphragm and into engagement with said pin in response to said impact thereby to fire said bursting charge in time delayed relation with respect to said impact.

References Cited in the file of this patent UNITED STATES PATENTS 190,861 Hotchkiss May 15, 1877 1,309,773 Newell July 15, 1919 1,311,104 Watson July 22, 1919 FOREIGN PATENTS 16,694 Great Britain of 1901 

